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Oct4-06, 02:48 PM
P: 163

The drawing shows a large cube(mass=25 kg) being accelerated accross a frictionless surface by a horizontal force P. A small cube(mass=4.0 kg) is in contact with the front surface of the large cube and will slide down unless P is sufficiently large. The coefficient of static friction between the cubes in 0.71. WHat is the smallest magnitude that P can have in order to keep the small cube from sliding downward?

What i did:

4.0 x 9.8 = 39.2 x 0.71 = 27.832 N
39.2 - 27.832 = 4.0a
a = 2.842 m/s/s

I do not know what the acceleration in the x direction must be in order to make the acceleration upward match 2.842.
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